EXPLANATION OF OCXIAN TEMPERATURE CHART No. 28. 



Isothermal lines connecting the series of light-hoase stations on the eastern coast of the United States, repre- 

 sented on Chart No. 1, constructed for every 5° of temperature, Fahrenheit, from 40° to 80°, inclusive, for the year 

 1883. 



The two isotherms of 55° follow one another closely at Petit Manan and Mount Desert Rock ; at MatinicuB Rock 

 the same temperature was recorded for two or three days, beginning August 9, and this point has been included in 

 the first isotherm of 55°. At Boon Island the isotherm of 60° was reached July 17 (that temperature, however, 

 continuing only until July 31), and at Thatcher's Island July 21, with no corresponding observations during the 

 period of falling temperature ; at Pollock Rip temperatures of 60° were occasionally recorded, but only for a day or 

 two at a time. At Fowey Rocks the temperature was above 75° from February 3 to March 3, after which there was 

 a period of lower temperature, continuing until April 1. At the Tortngas the temperatures of 75° and 80° were not 

 continuous between the dates on which the isotherms of 75° and 80° are plotted. 



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